Mixing apparatus, particularly for mixing of bleaching agents into cellulosic pulp



Nov. 8, 1966 .J. JOHAN N 3,284,055

MIXING APPA US, RTICU LY FOR MIXING OF BLEACHING AGE INTO CELLULOSIC PULP Filed July 2. 1964 5 SheetsSheet 1 IT L INVENTOR @iz fm Nov. 8, 1966 R. J. JOHANSEN 3,284,055

MIXING APPARATUS, PARTICULARLY FOR MIXING OF BLEACHING AGENTS INTO CELLULOSIC PULP Filed July 2, 1964 5 Sheets-Sheet 2 Nov. 8, 1966 R. J. JOHANSEN MIXING APPARATUS, PARTICULARLY FOR MIXING 0F BLEAGHING AGENTS INTO CELLULOSIC PULP 5 Sheets-Sheet 5 Filed July 2, 1964 IN V EN TOR.

United States Patent Office 3,284,055 Patented Nov. 8, 1966 MIXING APPARATUS, PARTICULARLY FOR MIX- ING OF BLEACHING AGENTS INTO CELLU- LOSIC PULP Rolf Jomar Johansen, Karlstad, Sweden, assignor to Aktiebolaget Kamyr, Karlstad, Sweden, :1 Swedish company Filed July 2, 1964, Ser. No. 379,910 Claims priority, application Sweden, July 5, 1963, 7,467/63 Claims. (Cl. 2597) The present invention relates to a mixing apparatus, particularly suited for mixing of bleaching agents into cellulosic pulp and which is of the kind comprising a casing having a cylindrical shell, and an agitating member enclosed in said casing and provided with fins, the pulp being charged through an inlet eccentrically located on said casing.

The object of the invention is to improve the agitating effect by such a design of the agitating member that the pulp is caused to tpulsate through the same. The essential characterizing feature of the invention consists in that the casing is provided with a wall set obliquely to the axis of the agitating member, and in that the agitating member consists of an apertured disk the periphery of which moves close to the cylindrical shell of the casing and which disk is located that close to said wall of the casing that the fins on that side of the disk extend over the greater part of the gap intermediate the disk and the wall, whereby pulp supplied through said eccentric inlet is caused to take part in the rotation of the agitating member and is drawn into said gap where the pulp, due to the varying width of said gap is partly pumped back and forth through the apertures of the disk, thus providing -a whirling motion of the pulp promoting its mixing with the bleaching agent.-

Some practical embodiments of the invention will be more closely described herein below with reference to the accompanying drawings.

FIGS. 1 and 2 refer to a mixing apparatus built together with the bottom of the bleach tower, FIG. 1 being a vertical sectional view thereof, and FIG. 2 being a horizontal sectional view taken along the line II-II in FIG. 1. FIG. 3 is an axial sectional view of a second embodiment of the mixing apparatus designed as a separate unit. A third embodiment is shown in FIGS. 4, 5 and 6, FIG. 4 being an axial sectional view, FIG. 5 a cross-sectional view taken along the line VV in FIG. 4, and FIG. 6 a cross-sectional view taken along the line VI-VI in FIG. 4.

The mixing apparatus shown in FIGS. 1 land 2 is inserted in the bottom of a bleach tower 11 (shown only in part), to which there are supplied through a conduit 13 cellulosic pulp and .a bleaching agent meant to react with the pulp in the tower. In order to secure a uniform bleaching it is import-ant that the bleaching agent is evenly distributed in the .pulp before it enters the tower where essentially no mixing takes place.

The mixing apparatus comprises a rotary agitating member 15, and .a casing enclosing the same, which casing forms a part of the bottom of the bleach tower. Said casing is formed by a cylindrical shell 17 merging at its upper part into a conical part of the bottom of the bleach tower, and a flat bottom end wall 19. The agitating member 15 is attached to a vertical shaft 21 which is coaxial to the cylindrical shell 17 of the casing. Said shaft is supported by bearings 23, 25, extends through the end wall 1 9 of the casing and is sealed thereto by means of a stufiing box 27. The end of the pulp supply conduit 13 forms a 90 tube bend which is connected to the end wall 19 at the side of the shaft 21 and which directs the supplied pulp substantially vertically upwards against the lower side of the agitating member 15.

The agitating member 15 consists of an essentially plane circular horizontal disk 29 set at right angles to the shaft 21 and having a hub 31 keyed to the upper end of said shaft 21. In the disk there are provided a great many through holes 33, which in the embodiment shown are shaped as arcuate slits and which put the spaces on opposite sides of the disk in communication with each other. The circumference of the disk moves close to the shell 17 and therefore the pulp can hardly pass the agitating member anywhere else than through said holes 33.

The plane end wall 19 is set obliquely to the shaft 21, i.e. forms an angle thereto different from 90. The inclination of the end Wall relatively to the horizontal plane may be of the order of 10 to 20, the angle relatively to the shaft thus being to Between the lower side 29 of the disk and the end wall 19 of the casing there is formed a gap, the width (or vertical extension) of which varies along the circumference. On its lower side the disk 29 is provided with a number of vertically and radially set fins 35. Said fins extend downwardly towards the end wall 19 and move with their lower edges only a small distance therefrom at the place where the gap is a minimum. Even at places where the gap is wider, as in the right-hand part of FIG. 1, the fins extend downwardly at least equal to half the height dimension of the gap. Therefore the fins catch the .pulp flowing vertically up through the conduit 13 and cause the same to take part in the horizontal circulating motion of the agitating member. Between adjacent fins 35 there are formed comparatively enclosed compartments in which successive small pulp batches are caught and carried around by the rotation of the agitating member. On account of the inclined position of the wall 19 the volume of the compartments decreases during the first half revolution of the agitating member and therefore the pulp will be forced up through the holes 33 in the disk 29, whereas the volume increases during the second half revolution and therefore the pulp is then sucked back through the hole-s 33. Due to the pulp being supplied under pressure through the conduit 13, a resulting flow is obtained which is directed upwards through the disk and further on into the bleach tower but the above described pumping action causes a superimposed pulsation back and forth which increases the turbulence of the flow and therefore brings about a thorough mixing of the bleach chemicals into the pulp.

Attached to the upper side of the agitating member 15 is a centrally located guiding member 37 in the form of a hopper (or a funnel-shaped tube) which forms an inlet open at its upper end and is connected at its lower part to diametrically opposed outlets 39, 41 which are directed outwardly and somewhat backwardly relatively to the direction of rotation of the disk 29. Thereby a centrifugal pump action is created forcing the pulp downwardly through the inlet hopper 37 and delivering the same close to the upper side of the disk 29 where it is mixed with pulp pulsating through the holes 33. One side wall 43, 45 of each outlet 39 or 41, respectively, is shorter than the other side wall, the latter preferably extending to the edge of the disk. The pressure drop formed behind the last-mentioned long wall assists the above-mentioned pumping action. In FIGURE 1 of the drawings, a plurality of projections 37a are shown extending generally radially from the exterior of the hopper 37 at the top of the hopper. These projections cause a stirring eifect that further aids in mixing the bleaching agent uniformly into the pulp. The projections 37a reduce peripheral movement of the pulp emanating in a backwards sense from the outlets 39, 41 and cause turbulence in the pulp due to the difference in motion of the emanating pulp and the projections 37a.

In FIG. 3, the .mixing apparatus is designed as a separate unit from which the pulp is supplied through a conduit to a bleach tower or similar. In said figure the same reference numerals have been used as in FIGS. 1 and 2 for corresponding items. The casing of the mixing apparatus has a cylindrical shell 17 and two end walls 19 and 20 which are both obliquely set to the shaft and are parallel to each other and located on the same average distance from the agitating member 15. Provided on the end wall 20 is an eccentrically located outlet 14 through which the pulp mixed with bleaching chemicals is discharged to a bleach tower or similar. The inlet 13 and the oulet 14 need not be placed on the end walls as shown, but may instead be placed on the cylindrical shell 17, preferably on the side where the gap between the apertured disk 29 and the end wall 19 or 20 is a maximum, and may be directed somewhat tangentially in the direction corresponding to the direction of rotation of the agitating member. In said case the orifices are preferably given oval or any other longitudinal shape in order to provide a sufficient area. The agitating member is provided with fins 35 on both sides and cooperates in a similar manner with the two end walls of the casing in order to get said abovedescribed pumping action.

In the embodiment of FIGS. 4, and 6 there is inserted between two similar agitating members 15, 16 a plane partition 22 attached to the casing and parallel to the end walls 19 and 20. On account of its oblique position said partition 22 cooperates with the agitating members 15 and 16 in exactly the same manner as the end Walls 19 and 20. The partition 22 may be regarded as one end wall of a section of a mixing apparatus composed of several sections each having its agitating member. For feeding pulp to the next section, holes 26, 28 are taken out of the partition 22, but the upper hole 28 extending out to the cylindrical shell of the casing in order to prevent gases from being trapped. Preferably the partition 22 is connected to a separate part 30 of the shell of the casing, which part can be disassembled. By removing said shell part together with one agitating member it is easy to rebuild the mixing apparatus into a simpler shape. Conversely, it is possible by inserting a further agitating member and a further shell part 30 with an inclined partition 22 to build up a mixing apparatus containing three sections which the pulp passes in succession.

The above described embodiments are merely examples, and the details thereof may be modified within the scope of the following claims.

I claim:

1. Mixing apparatus comprising a casing having a generally cylindrical shell and means defining a casing end wall, said end wall extending generally obliquely to the longitudinal axis of said shell; a rotatable agitator enclosed in said casing near said end wall and extending longitudinally therein, the agitator including at least one disk-like portion and means defining projections on said disk-like portion extending from one face thereof toward said oblique end wall a substantial portion of the distance between said disk-like portion and said oblique end wall, said disk-like portion having the periphery thereof generally adjacent said cylindrical shell and said disk-like portion including means defining at least one aperture communicating between the faces of said disk-like portion, inlet means for supplying material to be mixed to said casing eccentrically thereof between said oblique end wall and said disk-like portion; whereby material to be mixed, supplied through said inlet, is engaged by said projections and rotated by said agitator, said material being pulsated back and forth through said aperture by the interaction of said agitator and said oblique end wall.

2. Mixing apparatus as set forth in claim 1 further including means defining an open ended funnel-like guide on said agitator extending axially from the opposite face of said disk-like portion from said projections, said guide converging toward said disk-like portion and terminating adjacent said disk-like portion in means defining a plurality of radially outwardly and angularly rearwardly directed orifices with respect to the direction of rotation of said agitator whereby material returned through said guide during the rotation of said agitator is spread along the disklike member for mixing with material being pulsated through said aperture.

3. Mixing apparatus as set forth in claim 1 wherein said casing additionally includes a second end wall extending generally obliquely to the longitudinal axis of said shell, said second oblique end wall being adjacent the opposite face of said agitator disk-like portion from the first-mentioned oblique end Wall.

4. Mixing apparatus as set forth in claim 3 wherein said oblique end walls are substantially planar and mutually parallel.

5. Mixing apparatus as set forth in claim 1 wherein the agitator comprises a plurality of axially spaced, generally mutually parallel disk-like portions each including means defining at least one aperture communicating between the faces of each disk-like portion and having a plurality of projections extending axially from at least one face of each disk-like portion; and means defining at least one generally planar partition in said casing, one of said planar partitions being positioned between each pair of agitator disk-like portions, and means defining material passing apertures through each partition, each partition being peripherally secured to said casing cylindrical shell and extending substantially parallel to said oblique end wall.

References Cited by the Examiner UNITED STATES PATENTS l/l959 Dowling 259-8 X 6/1962 Reiffen 259-8 X 

1. MIXING APPARATUS COMPRISING A CASING HAVING A GENERALLY CYLINDRICAL SHELL AND MEANS DEFINING A CASING END WALL, SAID END WALL EXTENDING GENERALLY OBLIQUELY TO THE LONGITUDINAL AXIS OF SAID SHELL; A ROTATABE AGITATOR ENCLOSED IN SAID CASING NEAR SAID END WALL AND EXTENDING LONGITUDINALLY THEREIN, THE AGITATOR INCLUDING AT LEAST ONE DISK-LIKE PORTION AND MEANS DEFINING PROJECTIONS ON SAID DISK-LIKE PORTION EXTENDING FROM ONE FACE THEREOF TOWARD SAID OBLIQUE END WALL A SUBSTANTIAL PORTION OF THE DISTANCE BETWEEN SAID DISK-LIKE PORTION AND SAID OBLIQUE END WALL, SAID DISK-LIKE PORTION HAVING THE PERIPHERY THEREOF GENERALLY ADJACENT SAID CYLINDRICAL SHELL AND SAID DISK-LIKE PORTION INCLUDING MEANS DEFINING AT LEAST ONE APERTURE COMMUNICATING BETWEEN THE FACES OF SAID DISK-LIKE PORTION, INLET MEANS FOR SUPPLYING MATERIAL TO BE MIXED TO SAID CASING ECCENTRICALLY THEREOF BETWEEN SAID OBLIQUE END WALL AND SAID DISK-LIKE PORTION; WHEREBY MATERIAL TO BE MIXED, SUPPLIED THROUGH SAID INLET, IS ENGAGED BY SAID PROJECTIONS AND ROTATED BY SAID AGITATOR, SAID MATERIAL BEING PULSATED BACK AND FORTH THROUGH SAID APERTURE BY THE INTERACTION OF SAID AGITATOR AND SAID OBLIQUE END WALL. 